Wood chip concrete

NEWLY DEVELOPED WOOD-CHIP CONCRETE WITH... 

Keywords wood-chip concrete, recycling of used timber, special cement paste, injection method of cement paste, wood-chip packing ratio, strength, specific gravity, thermal conductivity... 

This paper deals with the reuse of used timber as wood-chip concrete which is made by injecting cement paste into the void of compacted wood-chip. It will be finding that a valuable building material could be made by the method developed by the authors. 

WOOD-CHIP CONCRETE WITH RECYCLED TIMBERS... 

The previous treatment on wood-chip made of used timber is necessary, because some wood release harmful extractives which delay the hydration of portland cement. Four kinds of previous treatment were tested, e.g. cold tap water, warm tap water (60 70°C), solutions of 0.1% NaOH and 0.5%NaOH. The strength test results of wood-chip concrete using these treated chip indicated almost the same, because the wood-chip used in this experiment were conifer so the harmful water-soluble extractives were little. After this result, tap water was used as a previous treatment liquid. 

The dimension of the wood-chip concrete specimens was 100x 100x400mm. The three pieces of specimens were made for each test, and the test result was given by the mean of them. 

Table 3 shows the test plan of wood-chip concrete. Fresh cement paste for injection was mixed by the double mixing method. The primary mixing water cement ratio was 0.23 and the chemical admixture was added to the primary water. 

Table 3. Test plan of wood-chip concrete...

Testing methods for wood-chip concrete were shown as below ... 

The relationship between the packing ratio of wood-chip and the bending strength of wood-chip concrete is shown in Fig. 5. At the age of 3 days and 7 days, the bending strength decreases linearly when the packing ratio is increased. 

The relationships between the curing age, the water cement ratio and the compressive strength of wood-chip concrete are shown in Fig. 6. The compressive strength increase linearly while the curing age increases from 3 to 91 days. The compressive strength becomes almost constant from the age of three months to six months except for the case of water cement ratio of 0.35. Fig. 6 shows that the compressive strength increases when water cement ratio decreases, but it is almost the same when water cement ratio are 0.40 and 0.35. 

Table 4. Compressive static modulus of elasticity of wood chip concrete unit 103MPa...

The apparent density of wood-chip concrete is fall into the range of 920 1250 kg/m3 under air drying condition. Table 5 and Table 6 show the specific strength and density of wood-chip concrete. 

The coefficient of linear thermal expansion of wood-chip concrete was measured by the push rod meter at JTCCM. The result of measurement is shown in Table 6. Because of the influence of moisture content, the coefficient of linear thermal expansion are different with the temperature range below and over 40°C. Within the range of -8 40°C, when the packing ratio of wood-chip is increased, the coefficient of linear thermal expansion increases. 

Table 6. Coefficient of linear thermal expansion of wood-chip concrete unit 10 6(1/K)...

Fig. 10 The packing ratio of wood-chip vs. nail pull out load of wood-chip concrete...

The nails were knocked into wood-chip concrete by a 500 gram hand hammer. The length of nails were 32, 50, 65 and 90 mm, and two third of the length were knocked into the wood-chip concrete. Fig. 9 shows the relationship between water cement ratio and the pull out load. The pull out load decreases when water cement ratio is increased, and the pull out load increases when the nail becomes larger. 

The wood-chip concrete with the packing ratio of 50, 60% and water cement ratio of 0.50, 0.60 can be sawed by a handy saw. 

The wood-chip concrete can be made by injecting cement paste into the void of wood-chip. 

The density of wood-chip concrete is in the range from 920 to 1250 kg/m3. 

The thermal conductivity of wood-chip concrete is 0.2 0.36 W/mK in the air dried state. 

The wood-chip concrete have a good work in nailing and sawing. 

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